JP2001276614A - Method of manufacturing photocatalytic active material for gas phase and photocatalytic active material for gas phase - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a manufacturing method for a photocatalytic active material for gas phase excellent in photocatalytic activity and capable of decomposing a harmful material in gas in a short time and to provide the photocatalytic active material for gas phase. SOLUTION: The photocatalytic active material for gas phase is manufactured by forming a photocatalyst layer containing the photocatalytic active material and bringing the photocatalyst layer into contact with the liquid containing water or forming the photocatalyst layer containing the photocatalytic active material and a water-retaining material and bringing the photocatalyst layer into contact with the liquid containing the water or putting the photocatalyst layer in an atmosphere containing moisture. In the photocatalytic active material for gas phase, the water content R expressed by formula (I) (Aw is the weight of the moisture in the photocatalyst layer, Ap is the weight of the photocatalytic active material) is >=1 wt.%. R(%)=[Aw/(Aw+Ap)]×100... (I).

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to a method for producing a photocatalytic active material for a gas phase and a photocatalytic active material for a gas phase.
More specifically, the present invention provides a method for efficiently producing a photocatalytically active material having excellent photocatalytic activity, for example, capable of treating harmful substances in a gas in a short time, and a gaseous phase having the above-mentioned excellent functions. The present invention relates to a photocatalytic active material for use.

[0002]

2. Description of the Related Art In recent years, with increasing interest in environmental problems, there has been an increasing demand for the removal of harmful substances that have an adverse effect on the human body and harmful substances such as odors in daily life. As a method for treating harmful substances, for example, (1) a method of adsorbing on an adsorbent and treating the adsorbent later, (2)
Methods of diluting and releasing into the environment, (3) methods of replacing contaminated substances (for example, soil, etc.) are known, and when recovering the environment, these means are actually used. Has been taken. However, these methods do not render harmful substances harmless, but only remove them for the time being, and cannot be said to be fundamental solutions.

Incidentally, it is known that certain metal compounds have a photocatalytic action. This photocatalytic action absorbs light energy to generate reactive species such as superoxide anion (.O ₂ ⁻ ) and hydroxyl radical (.OH), and as a result, oxidatively decomposes organic substances. Attempts are being actively made to apply antifouling, deodorization, antibacterial, sterilization, air purification, water purification, environmental purification, and the like using photocatalysis.

Examples of metal compounds having a photocatalytic action (hereinafter sometimes referred to as photocatalysts) include, for example, titanium dioxide, barium titanate (BaTi ₄ O ₉ ), strontium titanate (SrTiO ₃ ), and sodium titanate (N
a ₂ Ti ₆ O ₁₃ ), zirconium dioxide, cadmium sulfide, α-Fe ₂ O _{3 and the} like are known, and among these, titanium dioxide is typical.

It is known that when such a photocatalyst absorbs light, an extremely strong decomposing power is generated, and an organic substance is decomposed into carbon dioxide (CO ₂ ) and water (H ₂ O) by this action. . If the substance to be decomposed is a harmful organic substance, decomposing it into carbon dioxide and water means that the harmful substance is made harmless, and it is made harmless under mild conditions (only by irradiating light). For this reason, as a method for treating harmful organic substances, not only a gas phase system and a liquid phase system, but also a method for treating harmful organic substances using a photocatalyst attracts great attention and is being put to practical use.

When treating harmful substances, it is needless to say that the treatment can be performed in a shorter time. In the decomposition using a photocatalyst, in order to increase the processing speed, for example, (1) increase the irradiation light amount, (2) increase the amount of photocatalyst, (3) increase the reaction area, (4) heat, (5)
A method of increasing the oxygen concentration, (5) adding noble metal fine particles, and the like are often used. However, these methods can increase the processing speed to some extent, but have a limit, which leads to an increase in installation and operation costs, and cannot be said to be realistic in terms of cost.

[0007]

SUMMARY OF THE INVENTION Under such circumstances, the present invention provides a photocatalytic active material for a gaseous phase which has excellent photocatalytic activity and can decompose harmful substances in a gas in a short time. It is an object of the present invention to provide a well-produced method and a photocatalytically active material for a gas phase having the above-mentioned excellent functions.

[0008]

Means for Solving the Problems The inventors of the present invention have conducted intensive studies to achieve the above object, and as a result, contacting a photocatalytic layer containing a photocatalytic active substance with a liquid containing water, or By contacting the photocatalyst layer containing the substance and the water-retentive substance with a liquid containing water or placing it in an atmosphere containing moisture, a desired photocatalytic active material for a gas phase can be obtained. It has been found that a photocatalytic active material having a ratio of 1% by weight or more has excellent photocatalytic activity as a gas phase photocatalytic active material. The present invention has been completed based on such findings.

That is, the present invention provides (1) a method for producing a photocatalytic active material for a gas phase, which has a photocatalytic layer containing a photocatalytic active substance, and exhibits a decomposition action by the photocatalytic active substance in a gas phase. After forming the photocatalytic layer containing the photocatalytic active substance, a step of contacting the photocatalytic layer with a liquid containing water is performed. A method for producing a gas phase photocatalytic active material having a photocatalytic layer and exhibiting a decomposition action of the photocatalytic active material in a gas phase, comprising forming a photocatalytic layer containing the photocatalytic active material and a water retention material. Contacting the photocatalyst layer with a liquid containing water or placing the photocatalyst layer in an atmosphere containing water, and (3) a photocatalyst containing a photocatalytic active substance. Layers And, a decomposition action of the photocatalyst active substance in the gas phase photocatalytic activity material that exhibited in the gas phase,
In the photocatalyst layer, the formula (I) R (%) = [Aw / (Aw + Ap)] × 100 (I) (where, Aw is the weight of water in the photocatalyst layer, and Ap is the weight of the photocatalytic active substance in the photocatalyst layer) Wherein the water content R is 1% by weight or more.

[0010]

BEST MODE FOR CARRYING OUT THE INVENTION The process for producing a photocatalytically active material for a gas phase according to the present invention has a photocatalyst layer containing a photocatalytically active substance, and the photocatalyst for a gaseous phase exhibits a decomposition action by the photocatalytically active substance in the gas phase. A method for producing an active material, comprising two steps: (1) forming a photocatalyst layer containing the photocatalytically active substance and then contacting the photocatalyst layer with a liquid containing water (production method I) And (2) a method of forming a photocatalyst layer containing the photocatalytically active substance and the water-retaining substance, and then contacting the photocatalyst layer with a liquid containing water or placing it in an atmosphere containing water (manufacturing) There is a method II), whereby water is positively contained in the photocatalytic layer.

In the production methods I and II of the present invention, the substrate on which the photocatalytic layer is formed is not particularly limited in its material, and may be, for example, an organic polymer compound, paper, ceramic, glass, metal or the like. Materials can be used. The shape is not particularly limited, and any shape such as a plate, a sheet, a fiber, a honeycomb, a cylinder, a fiber, a rod, a sphere, and a particle can be used.

In the production methods I and II of the present invention,
Various types of photocatalytic active materials used in the catalyst layer
Conductor, eg TiO_Two, ZnO, SnO_Two, WO_Three, V_TwoO
_Five, CdO, Fe_TwoO_Three, In_TwoO_Three, ZrO_Two, KTa
O_Three, SrTiO_Three, Nb_TwoO_FiveOxide semiconductors such as C
dS, ZnS, PbS, WS_Three, In_TwoS_Three, Zn_xCd_(1
-x)S, CdS_xSe_(1-x)Such as sulfide semiconductors, Cd
Se, ZnSe, CdTe, ZnTe, PbSe, WS
e_ThreeChalcogenide semiconductors such as Si, S
Other semiconductors such as e, GaAs, Ga, etc.
Can be.

[0013] These photocatalytically active substances may be used alone or in combination of two or more. Among these photocatalytically active substances, oxide-based semiconductors and sulfide-based semiconductors are preferred, and oxide-based semiconductors are particularly preferred. The crystal structures of these semiconductors are not particularly limited. For example, in the case of TiO ₂ , there are anatase type, rutile type, brookite type and amorphous type, but any of them may be used, or a single type or a combination of two or more types may be used.

Examples of the form of the photocatalytically active substance include powdery (powder-like photocatalyst), slurry / dispersion type (liquid form in which the photocatalyst powder is suspended or dispersed in a solvent), and binder type (photocatalyst powder). And a heat treatment type (a liquid in which an organometallic compound containing a desired semiconductor metal component is dissolved in a solvent), and the like.

In the production method I of the present invention, a photocatalyst layer containing the photocatalytically active substance is formed on a substrate according to a conventional method, and then the photocatalyst layer is brought into contact with a liquid containing water to form the photocatalyst layer in the photocatalyst layer. Actively contain moisture.

On the other hand, in the production method II, metal oxides such as silica, alumina, iron oxide and zeolite can be used as the water retentive substance used in combination with the photocatalytically active substance. In order to increase the water holding capacity, these are preferably porous, fine particles, or layered. Further, clay minerals such as montmorillonite, beidellite, saponite, nontronite, hectorite, sauconite, and stevensite, layered polysilicate, layered perovskite, and the like can be used. These may be used alone or in combination of two or more. Also,
It is also possible to use a water-absorbing polymer or the like by interposing an inorganic water-retaining substance or the like between the photocatalytically active substance and the like.

When the water-retaining substance is contained in the photocatalyst layer together with the photocatalytic active substance, the amount used can be appropriately selected according to the desired water content, the type and form of the photocatalytic active substance, and the like. For example, the amount of the water-retaining substance is usually 0.1 to the total amount of the photocatalytically active substance and the water-retaining substance.
01 to 50% by weight, preferably 0.05 to 25% by weight,
More preferably, it is selected to be 0.1 to 20% by weight.

In the production method II of the present invention, a photocatalyst layer containing the photocatalytically active substance and the water-retaining substance is formed on a substrate according to a conventional method, and the photocatalyst layer is brought into contact with a liquid containing water. Alternatively, by placing the photocatalyst layer in an atmosphere containing moisture, moisture is positively contained in the photocatalyst layer.
In this way, a photocatalytically active material for a gas phase having excellent photocatalytic activity can be efficiently produced.

Next, the photocatalytically active material for a gas phase of the present invention will be described. The photocatalytic active material for a gas phase of the present invention has a photocatalytic layer containing the aforementioned photocatalytically active substance on the aforementioned base material, and is a material that exhibits a decomposition action by the photocatalytically active substance in the gas phase. The photocatalyst layer contains more water than the amount of water that has reached the adsorption equilibrium in the photocatalytic layer when the photocatalytic layer containing only the photocatalytic active substance is left at the temperature and humidity of the environment where the photocatalytic active material is used. It is necessary.

It is said that the decomposing power of the photocatalyst is generated by the oxidation or reduction of organic substances adsorbed on the surface by active oxygen species represented by the following formula.

[0021]

Embedded image

As apparent from these reaction formulas, it is understood that water (H ₂ O) and oxygen (O ₂ ) play important roles in addition to light. That is, in order to make the reaction proceed further and increase the reaction rate, it is sufficient to involve more decomposed substances together with more light, moisture and oxygen. Here, when attention is paid to the amount of water, the state in which the surface of the photocatalytically active material is covered with water during the reaction is considered to be the state where the water is the most abundant, but this rather prevents the participation of oxygen and decomposed substances. Results. What has been devised is a photocatalytic active material for a gas phase according to the present invention, characterized in that the water content of the photocatalyst layer is set to a certain value or more as described later. Therefore, in the present invention, the photocatalyst layer has the above-mentioned amount of water. The water content in the photocatalyst layer at this time is represented by the formula (I) R (%) = [Aw / (Aw + Ap)] × 100 (I) (where Aw is the weight of water in the photocatalyst layer, and Ap is the photocatalyst) R represents at least 1% by weight, preferably at least 5% by weight, more preferably at least 8% by weight. The upper limit is usually at most 40% by weight.

It is actually difficult to make the water content so that R is more than 40% by weight. In addition, when R exceeds 40% by weight, the effect of improving the photocatalytic activity is not so good for the amount. May not be recognized very much. Preferably 3
0% by weight or less, more preferably 20% by weight or less. The lower limit of R is 1% by weight. When the water content R is less than 1% by weight, the effect of improving the reaction rate cannot always be obtained. Here, the water content R does not exceed 1% by weight merely by leaving the photocatalyst layer in an atmosphere of high humidity, and in order to make the water content R of the photocatalyst layer 1% by weight or more, As described in the methods I and II for producing the photocatalytically active material for a gas phase, means must be taken to make the photocatalytic layer actively contain moisture.

In the photocatalytic active material for gas phase of the present invention, there is no particular limitation on the method for positively containing such an amount of water in the photocatalyst layer, and various methods can be used. According to the method shown, moisture can be contained in the photocatalyst layer extremely efficiently.

In the present invention, (1) a method in which a water-retentive substance is contained in a photocatalyst layer together with a photocatalytically active substance, and the photocatalytic layer is allowed to stand in a gas phase containing water or is brought into contact with a liquid containing water (the method of the present invention). Production method II), (2) a method in which a porous water-retaining material layer is provided above or below the photocatalyst layer and left in a water-containing gas phase or brought into contact with a water-containing liquid, or (3) A method in which a photocatalytic layer containing a photocatalytically active substance is brought into contact with a liquid containing water (the production method I of the present invention) is used.

In these methods, a porous substrate made of a water retention material can be used as the substrate. By using this porous substrate and bringing the substrate into contact with a liquid containing water, water can be continuously and efficiently supplied to the photocatalyst layer.

In the case of the above (3), the photocatalytically active substance itself is preferably porous. Therefore, in the present invention, in particular, the photocatalytic active substance used in the method (3) is preferably a powder baking method, a sol-gel method,
Those formed into a photocatalytic layer by a method such as a sputtering method and a vapor deposition method are preferable. In addition, even when the photocatalytically active substance is not porous, it is possible to obtain a desired water content by extending the contact time with a liquid containing water.

As the method (3), specifically, the following method can be used. (A) Immerse the photocatalyst layer in water. (B) The photocatalyst is brought into contact with fine particles containing water produced by an ultrasonic atomizer or the like. (C) Contacting water vapor generated by heating a liquid containing water with a photocatalyst. (D) bringing air containing water into contact with the cooled photocatalyst;

Further, a porous substrate comprising a water-retentive substance,
Alternatively, the thickness of the porous water-retaining material layer provided above or below the photocatalyst layer is usually 0.01 μm to 1 cm, preferably 0.05 μm to 1 mm, and more preferably 0.1 μm.
m to 100 μm. In addition, when forming a water retention material layer above or below a porous substrate made of a water retention material, or a photocatalytic layer, depending on the type of water retention material,
It may be formed using only a water retention material, or may be formed using a binder.

The thus-obtained photocatalytically active material for a gas phase of the present invention is excellent in photocatalytic activity and decomposes organic harmful substances in the atmosphere into carbon dioxide and water in a short time to render them harmless. It can be suitably used for environmental purification and the like.
When a water-retentive substance is used, the water-retentive substance can take in moisture in the atmosphere and keep the moisture in the photocatalyst layer at a certain level or more.

The photocatalytic active material for a gas phase according to the present invention comprises a light guide (glass) as a base material, a photocatalyst layer provided on the surface thereof, and a light (a wavelength for activating the photocatalytic active substance) on the light guide. The light can be applied to a photocatalyst filter that decomposes decomposed substances on the surface of the photocatalyst layer by introducing the light and leaking the photocatalyst layer. In this case, as a means for positively containing water in the photocatalyst layer, the method of the above (3) not using a water retention material, or a water retention material not absorbing light used for activating the photocatalytic active material is used. It is preferable to use

Examples of the water-retaining material that does not absorb light include pure silica gel. It is preferable to use such a water-retentive substance which does not absorb light, since the water-retentive substance can be provided below the photocatalyst layer to increase the surface area of the photocatalyst layer.

The photocatalytic device equipped with the photocatalytic active material for a gas phase according to the present invention is suitably used for decomposing and removing gas and fine particles of an organic substance in a gas. In order to decompose and remove the fine particles of the organic substance in the gas, the above-mentioned filter type is suitable.

That is, in the photocatalytic filter using the photocatalytic active material for a gas phase according to the present invention, a photocatalytic reaction is caused on the surface to generate a strong oxidizing power and a reducing power, and a substance collected by the filter is decomposed. Remove. As a trappable substance in a gas that can be decomposed and removed, for example, fume,
Examples include dust, atmospheric dust, tobacco smoke, dust, viruses, bacteria, malodorous substances (acetaldehyde, methyl mercaptan, etc.), harmful substances (trichloroethylene, tetrachloroethylene, benzene, toluene, etc.).

The photocatalyst filter is prepared by forming projections on the surface of a photocatalytic active material for a gas phase of the present invention using a substrate having a fiber, plate, sheet or other shape and bundling them. What was done is suitable.
In such a photocatalytic filter, granules made of the water-retaining material can be used as the projections. In this case, particles of the water-retaining material that does not absorb light used to activate the photocatalytically active material can be used. And a structure that also serves as a protrusion and a water-retaining material can be used.

This photocatalytic filter is, for example, a diesel particulate filter (DPF) for removing black smoke contained in exhaust gas of a diesel engine and solid particulate matter (particulate) composed of unburned hydrocarbons and lubricating oil. It can be suitably used as a gas treatment filter (for example, an air filter for a clean room, an air purifier) and the like.

[0037]

Next, the present invention will be described in more detail with reference to examples, but the present invention is not limited to these examples.

The concentration of the organic substance and the water content in the photocatalyst layer were measured according to the following methods. (1) Concentration of organic substance The concentration of the organic substance was measured by gas chromatography. In addition, the point in time when detection was no longer performed by the gas chromatograph was defined as concentration 0. The equipment and conditions used for the analysis are as follows. Apparatus: Gas chromatograph BC-14B (Shimadzu Corporation) Detector: FID Column: SBS-120 (Shimadzu Corporation) Temperature: Detector temperature 200 ° C Vaporization chamber temperature 200 ° C Column oven temperature 100 ° C Organic in this example A substance concentration of x ppm is defined as 1 m ^{3 of} gas.
It means that an organic substance gas is contained therein in xcm ³ .

(2) Water content R of the photocatalyst layer The water content R was measured using a thermogravimetric analyzer [“TG81” manufactured by Rigaku Corporation.
10 "] and was calculated as follows. The TiO ₂ powder placed in the sample cup was set on the device,
The temperature was raised to 100 ° C. at a rate of one minute and maintained at that temperature for one hour. The difference between the weight of the sample before the temperature was raised and the weight after being held at 100 ° C. for 1 hour was defined as the water content, and the water content R was calculated using the above-described formula (I).

COMPARATIVE EXAMPLE 1 TiO ₂ fine particle slurry [Tainok H manufactured by Taki Kagaku Co., Ltd.]
-30] was spin-coated at 3000 rpm for 15 seconds and applied to a glass substrate, and then heat-treated at 500 ° C. for 2 hours. This operation was repeated once to obtain a 2.5 μm thick substrate with a TiO ₂ film. This was set in a batch-type reactor, and the humidity of the closed vessel was set to 50 RH%. At this time, the water content R of the photocatalyst layer was 0.9% by weight.

Next, a saturated gas of benzene was injected into the container to adjust the benzene concentration to 25 ppm. Under stirring, benzene was decomposed using black light blue as a light source.
The irradiation light amount at this time was 1.8 mW / cm ² , and the center wavelength was 352 nm. The results are shown in FIG. Time from the start of irradiation until the benzene concentration becomes 0 (hereinafter, T
Called ₀ . ) Was 430 minutes.

Example 1 A glass substrate with a TiO ₂ film prepared under the same conditions as in Comparative Example 1 was placed in ion-exchanged water, left at room temperature for 3 hours in a dark place, taken out, and left at room temperature for 1 hour. Let dry. The water content R of the photocatalyst layer after drying was 11.8% by weight. Using this glass substrate with a TiO ₂ film, degradation of benzene was evaluated in the same manner as in Comparative Example 1. The results are shown in FIG. T _{0 under} this condition is 70
Minutes, and the decomposition time was greatly shortened to about 1/6 as compared with the case where water was not used.

Example 2 TiO ₂ fine particle slurry [Tainock H manufactured by Taki Kagaku Co., Ltd.
-30], silica gel fine particles [Microid ML-836 manufactured by Tokai Chemical Industry Co., Ltd.] were added and dispersed so as to be 10% by weight with respect to the total amount of the TiO ₂ fine particles.
This coating solution was spin-coated at 3500 rpm for 30 seconds and applied to a glass substrate, and then heat-treated at 500 ° C. for 2 hours to obtain a 1.7 μm-thick silica gel-containing substrate with a TiO ₂ film. The silica gel-containing substrate with a TiO ₂ film was allowed to absorb water by leaving it at room temperature under a humidity of 50 RH% overnight. At this time, the water content R of the photocatalyst layer was 5.
It was 5% by weight. Next, the decomposition characteristics of benzene were evaluated in the same manner as in Comparative Example 1. T of this thing
₀ was 100 minutes, and benzene was able to be treated in about 1/4 of the time without silica gel.

Example 3 TiO ₂ fine particle slurry [Tainock H manufactured by Taki Kagaku Co., Ltd.
−30], montmorillonite [Bengel manufactured by Toyohyun Yoko Co., Ltd.] was added and dispersed in an amount of 5% by weight with respect to the total amount of the TiO ₂ fine particles. 3500 of this coating solution
After spin-coating at 60 rpm for 60 seconds and applying to a glass substrate, heat treatment was performed at 500 ° C. for 2 hours to a thickness of 1.9 μm.
m of a substrate with a montmorillonite-containing TiO ₂ film was obtained.
The montmorillonite-containing TiO ₂ film-coated substrate was allowed to absorb water by being left at room temperature under a humidity of 100 RH% (saturated steam) for 5 hours. At this time, the water content R of the photocatalyst layer was 8.5% by weight. Next, the decomposition characteristics of benzene were evaluated in the same manner as in Comparative Example 1. This product had a T ₀ of 80 minutes, and was able to process benzene in about な い of the time without montmorillonite.

Example 4 Tetraethoxysilane, 0.15 mol / liter aqueous hydrochloric acid, isopropanol and polyethylene glycol #
2000 were mixed at a weight ratio of 100: 35: 126: 29 to prepare a silica sol. This sol is applied to a glass substrate and heat-treated at 500 ° C. for 1 hour to have a thickness of about 1 μm.
m of porous silica film was formed. On this porous silica film, a TiO ₂ photocatalyst was applied to form a 1.8 μm-thick photocatalyst layer. This was allowed to stand at room temperature under a humidity of 100 RH% (saturated steam) for 5 hours to absorb water.
At this time, the water content R of the photocatalyst layer was 9.0% by weight. Next, the decomposition characteristics of benzene were evaluated in the same manner as in Comparative Example 1, and the T ₀ was 90 minutes. About 1% less than that without a porous silica membrane
The benzene could be treated in a time of / 5.

Example 5 The substrate provided with the silica gel-containing TiO ₂ film obtained in Example 2 was
After irradiating with ultraviolet light for 3 hours at room temperature in distilled water, it was taken out and left to dry at room temperature for 1 hour. The water content R of the photocatalyst layer after drying was 12.5% by weight.
Next, when the decomposition characteristics of benzene were evaluated by the same method as in Comparative Example 1, the T ₀ was 70 minutes. Benzene could be treated in about 1/6 of the time without silica gel.

Comparative Example 2 Benzene was decomposed in the same manner as in Comparative Example 1 except that the humidity of the container was changed to 0 RH%. Its T ₀ was 850 minutes. The water content R of the photocatalyst layer was 0.8% by weight.

Example 6 The substrate provided with the silica gel-containing TiO ₂ film obtained in Example 2 was
After 3 hours at room temperature in distilled water in a dark place, it was taken out and allowed to dry at room temperature for 1 hour. The water content R of the photocatalyst layer after drying was 12.0% by weight. next,
When the benzene decomposition characteristics were evaluated under the same conditions as in Comparative Example 2, T ₀ was 200 minutes. The treatment could be performed in about 1/4 of the time without silica gel.

Comparative Example 3 Decomposition of acetaldehyde was performed in the same manner as in Comparative Example 1 except that the benzene concentration was changed from 25 ppm to acetaldehyde concentration of 150 ppm, and T ₀ was 60 minutes.

Example 7 Acetaldehyde was decomposed in the same manner as in Example 3 except that the benzene concentration was changed from 25 ppm to acetaldehyde concentration of 150 ppm. As a result, T ₀ was 30 minutes. Acetaldehyde was able to be treated in half the time as compared with the case not containing montmorillonite.

[0051] In Comparative Example 4 Comparative Example 1, except for changing the concentration of toluene 25ppm benzene concentration 25ppm, was subjected to decomposition of toluene in the same manner as in Comparative Example 1, T ₀ was 460 minutes.

[0052] In Example 8 Example 2, except for changing the concentration of toluene 25ppm benzene concentration 25ppm, was subjected to decomposition of toluene in the same manner as in Example 2, T ₀ was 70 minutes. Toluene could be treated in about 1/7 the time without silica gel.

[0053] In Comparative Example 5 Comparative Example 1, except for changing the 150ppm from 25ppm initial concentration of benzene was subjected to decomposition of benzene in the same manner as in Comparative Example 1, T ₀ was 47 hours.

[0054] In Example 9 Example 2, except for changing the 150ppm from 25ppm initial concentration of benzene was subjected to decomposition of benzene in the same manner as in Example 2, T ₀ was 18 hours. Benzene could be treated in about 2/5 of the time without silica gel. The above results are summarized in Tables 1 and 2.

[0055]

[Table 1]

[0056]

[Table 2]

Reference Example Using a glass substrate with a TiO ₂ film produced under the same conditions as in Comparative Example 1, the humidity in the container was set to 0, 28, 50, 66, 10
0 RH%, the benzene concentration was 10 ppm,
The decomposition of benzene was evaluated in the same manner as in Comparative Example 1. In this case, the water content of the TiO ₂ film was all less than 1% by weight. Further, the glass substrate provided with a TiO ₂ film was subjected to water treatment in the same manner as in Example 1, and then the degradation of benzene was evaluated in the same manner as described above under the condition of a humidity of 50 RH%. At this time, the water content of the TiO ₂ film was 10.5% by weight.
FIG. 2 is a graph showing the relationship between the irradiation time and In (benzene concentration). From this figure, it can be seen that increasing the water content in the photocatalyst layer is effective for improving the photocatalytic activity.

[0058]

The photocatalytic active material for gas phase of the present invention is a material in which water is positively contained in the photocatalyst layer, has excellent photocatalytic activity, and is capable of decomposing harmful substances in gas in a short time. It can be detoxified and is suitably used for environmental purification and the like. Further, according to the method of the present invention, the photocatalytic active material for a gas phase can be efficiently and inexpensively produced.

[Brief description of the drawings]

FIG. 1 shows irradiation time and l in Comparative Example 1 and Example 1.
4 is a graph showing a relationship with n (benzene concentration).

FIG. 2 is a graph showing a relationship between irradiation time and ln (benzene concentration) when the water content in the photocatalyst layer is different in a reference example.

──────────────────────────────────────────────────の Continued on the front page (51) Int.Cl. ⁷ Identification symbol FI Theme coat ゛ (Reference) B01J 21/16 F01N 3/08 C 35/02 B01D 53/36 J F01N 3/02 301 ZABG 3/08 104B F-term (for reference) 3G090 AA06 3G091 AA18 AB01 AB13 BA20 GA01 GA02 GA03 GA04 GA05 GA06 GB01X GB10W GB16X GB17X GB19X 4D048 AA11 AA14 AA18 AA19 AA21 AA22 AA23 AB01 AB02 AB03 BA06X BA07X BA09 ABA04A03 BA03 A03BA03 A03 BA04 A03 BA08 BA10B BA48A CA02 CA03 CA07 CA08 CA10 CA15 CA17 CA18 CA19 DA05 EA07 EC27 ED04 FA03 FB02 FB23

Claims (5)

[Claims] 1. A photocatalyst layer containing a photocatalytically active substance,
A method for producing a photocatalytically active material for a gas phase in which a photocatalytically active substance is decomposed in a gaseous phase, comprising forming a photocatalyst layer containing the photocatalytically active substance, and then contacting the photocatalyst layer with a liquid containing water. A process for producing a photocatalytically active material for a gas phase, comprising the step of: 2. A photocatalyst layer containing a photocatalytically active substance,
A method for producing a photocatalytically active material for a gaseous phase in which the photocatalytically active substance is decomposed in a gaseous phase, comprising forming a photocatalyst layer containing the photocatalytically active substance and a water-retaining substance,
A method for producing a photocatalytically active material for a gas phase, comprising a step of bringing the photocatalyst layer into contact with a liquid containing water or placing it in an atmosphere containing moisture. 3. A photocatalyst layer containing a photocatalytically active substance,
A photocatalytically active material for a gaseous phase, which exhibits a decomposition action of the photocatalytically active substance in a gaseous phase, wherein R (%) = [Aw / (Aw + Ap)] × 100 (I) (Where Aw represents the weight of water in the photocatalyst layer, and Ap represents the weight of the photocatalytic active substance in the photocatalyst layer.) The water content R represented by 1% by weight or more is characterized by being not less than 1% by weight. Active material. 4. The photocatalytic active material for a gas phase according to claim 3, wherein the photocatalytic layer further contains a water-retentive substance together with the photocatalytic active substance. 5. The photocatalytic active material for a gas phase according to claim 3, wherein the water content R is 40% by weight or less.